Reference electrodes are used in potentiometric analysis of qualitative and/or quantitative analyses of ions in solution. There are a variety of such electrodes, utilizing different electrode chemistry, including silver/silver chloride, calomel, and mercury/mercurous sulfate electrodes, as examples. Generally, such reference electrodes use internal aqueous electrolyte solutions and are designed and intended for long-term, repeated use.
A liquid junction-free reference electrode system is described in “Solvent-Processible Polymer Membrane-Based Liquid Junction-Free Reference Electrode,” by Hyuk Jin Lee et al., Anal. Chem. 70, pages 3377-3383 (1998). Therein, the authors describe the use of solvent-processible polymer membranes for forming liquid junction-free reference electrodes in a planar solid-state format. A polyurethane matrix reference site was formed on an aluminum oxide onto which silver electrodes were printed by incorporating both cation- and anion-exchange sites (for example, potassium tetrakis(p-chlorophenyl)borate and tridodecylmethylammonium chloride) into a polyurethane matrix, and dispensing (screen-printing) a small volume of this material, typically 5 μL, onto the silver electrode and the surrounding dielectric layer. The sensors were dried in ambient air for 12 h.
In “Disposable Reference Electrode” by A. Mroz et al., Analyst 123, pages 1373-1376 (1998), the authors describe a disposable reference electrode which includes an Ag/AgCl electrode without a diaphragm, where an internal electrolyte KCl aqueous solution is enclosed in a glass-fiber filter medium in contact with a screen-printed Ag/AgCl strip conductor. The lower part of the electrode is cut open before the electrode is used.
Accordingly, it is an object of the present invention to provide stable reference electrodes which do not require calibration.
Another object of the invention is to provide inexpensive, disposable and stable reference electrodes which do not require calibration.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.